<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div class="box1">
        <div class="box2"></div>
    </div>
</body>
<style>
    body {
        height: 200px;
        position: relative;
    }

    .box1 {
        width: 500px;
        height: 500px;
        border: 1px solid blueviolet;
        margin: 200px;
        /* position: relative; */
    }

    .box2 {
        width: 100px;
        height: 100px;
        background: pink;
        position: fixed;
        left: 0;
        top: 0;
    }
</style>

</html>